Thresholds for hanger slackening and cable shortening in the Melan equation for suspension bridges

The Melan equation for suspension bridges is derived by assuming small displacements of the deck and inextensible hangers. We determine the thresholds for the validity of the Melan equation when the hangers slacken, thereby violating the inextensibility assumption. To this end, we preliminarily study the possible shortening of the cables: it turns out that there is a striking difference between even and odd vibrating modes since the former never shorten the cables. These problems are studied both on beams and plates

Role of the transcription factor Erg in inflammation

Pro-inflammatory and atherogenic stimuli up-regulate the expression of endothelial adhesion molecules which support the extravasation of leukocytes into the sub-endothelial space. This process drives plaque progression and contributes to its complications. Erg is an ETS transcription factor constitutively expressed in EC which regulates angiogenesis and endothelial homeostasis. Recently, Erg was shown to inhibit endothelial expression of the chemokine IL-8. In EC, Erg expression is down-regulated by the pro-inflammatory cytokine TNF-alpha, through a mechanism which appears to involve Erg protein degradation. These data suggest that Erg may be involved in inflammation. To test this hypothesis, I modulated Erg expression in HUVEC by inhibition with antisense or over-expression using adenovirus encoding for Erg (AdErg). Basal ICAM-1 expression was up-regulated following Erg inhibition, and down-regulated by Erg over-expression. Both of these effects were transcriptional, as shown by a luciferase reporter assay. Over-expression of Erg could inhibit TNF-dependent up-regulation of ICAM-1 and ICAM-1 promoter activity. Thus Erg acts as a transcriptional repressor of ICAM-1 expression in resting and activated EC. This pathway involves NF-kB, since both basal and TNF-α-induced NF-kB activity was repressed by AdErg, and Erg over-expression inhibited the TNF-α induction of NF-kB p65 phosphorylation. In vitro, Erg over-expression led to decreased adhesion of leukocytes to TNF-stimulated HUVEC. In vivo, local injection of AdErg in the mouse paw resulted in reduction of TNF-α-induced inflammation. Interestingly, staining of human coronary artery plaques showed that Erg is absent from activated endothelium over the vulnerable region of the plaque. In conclusion, I propose that Erg exerts a protective role in the endothelium by repressing pro- inflammatory signaling and gene expression. These results suggest a novel approach to anti-inflammatory therapies

Pojava parazita Otodistomum veliporum u štrcalu morskog psa drkovne (Dalatias licha)

The presence of the digenean Otodistomum veliporum is reported here for the first time as a parasite in the spiracle of a Mediterranean specimen of the kitefin shark Dalatias licha.Prvi put je zabilježena u znanstvenoj literaturi prisutnost parazita Otodistomum veliporum u štrcalu morskog psa drkovne Dalatias licha

New record of the great white shark Carcharodon carcharias from Lampedusa

This new record confirms that the Central Mediter ranean, and Sicilian coasts in particular, still represent a key area for the population of Mediterranean white sharks, but also for other shark species (Bilecenoglu et al., 2013); in fact, 43% of all white shark sightings in the Italian seas (Micarelli et al., 2011) are from this area

Genetic differentiation and phylogeography of Mediterranean-North Eastern Atlantic blue shark (Prionace glauca, L. 1758) using mitochondrial DNA: Panmixia or complex stock structure?

Background The blue shark (Prionace glauca, Linnaeus 1758) is one of the most abundant epipelagic shark inhabiting all the oceans except the poles, including the Mediterranean Sea, but its genetic structure has not been confirmed at basin and interoceanic distances. Past tagging programs in the Atlantic Ocean failed to find evidence of migration of blue sharks between the Mediterranean and the adjacent Atlantic, despite the extreme vagility of the species. Although the high rate of by-catch in the Mediterranean basin, to date no genetic study on Mediterranean blue shark was carried out, which constitutes a significant knowledge gap, considering that this population is classified as “Critically Endangered”, unlike its open-ocean counterpart. Methods Blue shark phylogeography and demography in the Mediterranean Sea and North-Eastern Atlantic Ocean were inferred using two mitochondrial genes (Cytb and control region) amplified from 207 and 170 individuals respectively, collected from six localities across the Mediterranean and two from the North-Eastern Atlantic. Results Although no obvious pattern of geographical differentiation was apparent from the haplotype network, Φst analyses indicated significant genetic structure among four geographical groups. Demographic analyses suggest that these populations have experienced a constant population expansion in the last 0.4–0.1 million of years. Discussion The weak, but significant, differences in Mediterranean and adjacent North-eastern Atlantic blue sharks revealed a complex phylogeographic structure, which appears to reject the assumption of panmixia across the study area, but also supports a certain degree of population connectivity across the Strait of Gibraltar, despite the lack of evidence of migratory movements observed by tagging data. Analyses of spatial genetic structure in relation to sex-ratio and size could indicate some level of sex/stage biased migratory behaviour

Observations about surface behaviour of the great white shark Carcharodon carcharias (L.) in presence of passive preys at Dyer Island (Southafrica)

During 4 study expeditions in SouthAfrica, performed in 2000, 2003, 2004 and 2005, observations about surface predatory behaviour of the Great White Shark in presence of passive preys were made. Observations were carried out by Unlimited Shark Diving boats and by cage diving around Dyer Island, about 5 miles far from Gansbaai. During the 27 observation days were identified 78 different specimens, that exhibited 8 different behaviours. The Great White Shark population observed around Dyer island shows a greater variety of behaviours than the population studied along the California coasts

Solenoidal extensions in domains with obstacles: explicit bounds and applications to Navier-Stokes equations

We introduce a new method for constructing solenoidal extensions of fairly general boundary data in (2d or 3d) cubes that contain an obstacle. This method allows us to provide explicit bounds for the Dirichlet norm of the extensions. It runs as follows: by inverting the trace operator, we first determine suitable extensions, not necessarily solenoidal, of the data; then we analyze the Bogovskii problem with the resulting divergence to obtain a solenoidal extension; finally, by solving a variational problem involving the infinity-Laplacian and using ad hoc cutoff functions, we find explicit bounds in terms of the geometric parameters of the obstacle. The natural applications of our results lie in the analysis of inflow-outflow problems, in which an explicit bound on the inflow velocity is needed to estimate the threshold for uniqueness in the stationary Navier-Stokes equations and, in case of symmetry, the stability of the obstacle immersed in the fluid flow